<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="lib/vue.js"></script>
</head>
<body>
    <div id="app">
        <input type="text" v-model="n1">
        <select v-model="opt">
            <option value="+">+</option>
            <option value="-">-</option>
            <option value="*">*</option>
            <option value="/">/</option>

        </select>
        <input type="text" v-model="n2" >

        <input type="button" value="=" @click="calc">

        <input type="text" v-model="result">



    </div>
    <script>
           new Vue({
                el:'#app',
                data: {
                   n1:0,
                   n2:0,
                   result:0,
                   opt:'+'

                },
              methods:{
                    calc(){
                       switch(this.opt){
                            case '+':
                                this.result=parseInt(this.n1)+parseInt(this.n2)
                                   break;
                            case '-':
                                 this.result=parseInt(this.n1)-parseInt(this.n2)
                                    break;
                            case '*':
                                this.result=parseInt(this.n1)*parseInt(this.n2)
                                     break;
                            case '/':
                                this.result=parseInt(this.n1)/parseInt(this.n2)
                                    break;
                        }
                        //快捷方法，开发中尽量少用
                        /*var codeStr= 'parseInt(this.n1)' + this.opt+'parseInt(this.n2)'
                        this.result=eval(codeStr)*/

                    }
                }
            });
        </script>
    
</body>
</html>